The present invention addresses a need in the art to simplify assembly and enhance operation of print engine components that interact with a printing substrate to ensure constant, steady advancement of the printing media relative to one or more print heads. In large format ink jet print engines a plurality of rollers driven by an axial shaft have heretofore been highly toleranced, multi-component parts. The axial shaft itself is typically fabricated to minimize tolerance run-out and is supported on at least two (2) bearing assemblies coupled to each end of the axial shaft. Thus, as a result of the need for precision parts, and tight dimensional tolerances, the assembly of such prior art grit rollers has been a tedious part of building quality paper drive mechanisms. The function of such complex prior art drive mechanisms thus relies primarily on tightly toleranced engineering design, precise part fabrication, and nimble component assembly skills. Each of these needs and requirements add cost, complexity, and assembly time for the successful performance of these diverse tasks to ultimately produce a smooth running, quality end product.
The basic design criteria for driving a printing media with sets of grit rollers and nip rollers are simple. As long as each grit roller is sized equally, the axial shaft is perfectly straight, the bearings supporting the axial shaft operate smoothly, and the final assembly of all parts is completed as planned, the grit roller will consistently cooperate with a corresponding nip roller to form a discrete driving footprint for propelling the printing media at a constant velocity.
In the prior art many discrete piece parts are typically used in the installation and operation of these critical grit roller bearings. A significant obstacle to reducing cost and assembly efforts for prior art roller mechanisms lies in the abundance of parts of the prior art roller bearings, since inventory, assembly, service, and replacement operations are all negatively impacted. For example, in the exemplary embodiment taught herein a single axial shaft spans an internal compartment in a large format ink jet printer having a platen/printing zone of between three feet (3') and six feet (6') wide. The axial shaft thus drives a plurality of grit rollers in cooperation with corresponding nip rollers that in prior art systems would require that the axial shaft possess an extremely high final machined tolerance. The cost of highly machined axial shafts coupled with the assembly and service complexity of prior art grit roller assemblies, and specifically, bearings are both positively impacted when replaced by the apparatus of the present invention.
The present invention thus finds utility over a variety of printing platforms that operate to simply and accurately propel each roller at a desired location in apertures formed in a printing platen without regard to any tolerance run-out of an axial shaft used to drive the rollers and with a minimum of individual parts needed for final assembly.